The members of the Children's Cancer Study Group, using mutually agreed upon protocols, conduct clinical investigations regarding optimal therapy of children with leukemia and solid tumors. The aim of such protocols is to evaluate therapeutic regimens, often combining surgery, radiotherapy, and chemotherapy, in an effort to increase disease-free survival and improve the cure rate of these illness. In addition, information regarding supportive care, use of blood products, toxicity, and survival is gathered and evaluated.